Back contact photovoltaic module with glass back-sheet

ABSTRACT

An integrated back sheet for a back-contact solar cell module and a back-contact solar cell module made with an integrated glass back-sheet are provided. Processes for making such integrated back-sheets and back-contact solar cell modules are also provided. Elongated electrically conductive wires are mounted on a layer of the integrated back-sheet adhered to the glass back-sheet. The elongated electrically conductive wires of the integrated back-sheet electrically connect to solar cell back contacts when the back-sheet is used in a back-contact photovoltaic module.

FIELD OF THE INVENTION

The present invention relates to back-contact photovoltaic modules withglass back-sheets, and to processes for making such photovoltaic moduleswith conductive circuitry integrated into the modules.

BACKGROUND

A photovoltaic cell converts radiant energy, such as sunlight, intoelectrical energy. In practice, multiple photovoltaic cells areelectrically connected together in series or in parallel and areprotected within a photovoltaic module or solar module.

As shown in FIG. 1, a photovoltaic module 10 typically comprises alight-transmitting front sheet substrate 12, a front encapsulant layer14, an active photovoltaic cell layer 16, a rear encapsulant layer 18and a back-sheet 20. The light-transmitting front sheet substrate may becomprised of glass or plastic, such as, polycarbonate, acrylic,polyacrylate, cyclic polyolefin, polystyrene, polyamide, polyester,silicon polymers and copolymers, fluoropolymers and the like, andcombinations thereof. The front and back encapsulant layers 14 and 18adhere the photovoltaic cell layer 16 to the front and back sheets, theyseal and protect the photovoltaic cells from moisture and air, and theyprotect the photovoltaic cells against physical damage. The encapsulantlayers 14 and 18 are typically comprised of a thermoplastic orthermosetting resin such as ethylene-vinyl acetate copolymer (EVA). Thephotovoltaic cell layer 16 is made up of any type of photovoltaic cellthat converts sunlight to electric current such as single crystalsilicon solar cells, polycrystalline silicon solar cells,microcrystalline silicon solar cells, amorphous silicon-based solarcells, copper indium (gallium) diselenide solar cells, cadmium telluridesolar cells, compound semiconductor solar cells, dye sensitized solarcells, and the like. The back-sheet 20 provides structural support forthe module 10, it electrically insulates the module, and it helps toprotect the module wiring and other components against the elements,including heat, water vapor, oxygen and UV radiation. The module layersneed to remain intact and adhered for the service life of thephotovoltaic module, which may extend for multiple decades. Thephotovoltaic cells typically have electrical contacts on both the frontand back sides of the photovoltaic cells. However, contacts on the frontsunlight receiving side of the photovoltaic cells can cause up to a 10%shading loss.

In back-contact photovoltaic cells, all of the electrical contacts aremoved to the back side of the photovoltaic cell. With both the positiveand negative polarity electrical contacts on the back side of thephotovoltaic cells, electrical circuitry is needed to provide electricalconnections to the positive and negative polarity electrical contacts onthe back of the photovoltaic cells. U.S. Patent Application No.2011/0067751 discloses a back contact photovoltaic module with aback-sheet having patterned electrical circuitry that connects to theback contacts on the photovoltaic cells during lamination of the solarmodule. The circuitry is formed from a metal foil that is adhesivelybonded to a carrier material such as polyester film or Kapton® film. Thecarrier material may be adhesively bonded to a protective layer such asa Tedlar® fluoropolymer film. The foil is patterned using etchingresists that are patterned on the foil by photolithography or by screenprinting according to techniques used in the flexible circuitryindustry. The back contacts on the photovoltaic cells are adhered to andelectrically connected to the foil circuits by adhesive conductivepaste. There is a need for alternative back-contact photovoltaic modulesin which conductive circuitry is integrated with a rigid glassback-sheet. There is also a need for moisture impermeable back-sheetsthat maintain moisture integrity for the long service life of thephotovoltaic modules which may extend for decades. There is also a needfor photovoltaic back contact modules in which the back contactssecurely attach to the conductive circuitry and remain securely attachedfor multiple decades.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description will refer to the following drawings which arenot drawn to scale and wherein like numerals refer to like elements:

FIG. 1 is cross-sectional view of a conventional solar cell module.

FIGS. 2 a and 2 b are schematic plan views of the back side of arrays ofback-contact solar cells.

FIGS. 3 a and 3 b are schematic representations of back-sheets withintegrated wire circuits.

FIG. 4 a is a plan view of a wire mounting layer with adhered conductivewires, and FIG. 4 b is a plan view of the wire mounting layer after theconductive wires have been selectively cut.

FIG. 5 a is a plan view of a an interlayer dielectric (ILD), and FIG. 5b is a plan view of the ILD in which holes or openings have been formedor cut out.

FIGS. 6 a-6 e are cross-sectional views illustrating one disclosedprocess for forming a back-contact solar cell module in which integratedconductive wires are connected to the back contacts of solar cells.

FIG. 7 is a cross-sectional view illustrating one disclosed process forforming a back-contact solar cell module in which integrated conductivewires are connected to the back contacts of solar cells.

FIGS. 8 a and 8 b are cross-sectional views illustrating one disclosedprocess for forming a back-contact solar cell module in which integratedconductive wires are connected to the back contacts of solar cells.

FIG. 9 a is a plan view of a polymeric wire mounting layer, and FIG. 9 bis a plan view of the wire mounting layer in which holes or openingshave been formed or cut out. FIGS. 9 c illustrates the application ofconductive wires to the wire mounting layer, and FIG. 9 d illustratesthe application of a polymeric layer over the conductive wires.

FIGS. 10 a-10 f illustrate steps of a process for forming a back-contactsolar cell module in which an array of back-contact solar cells areelectrically connected in series by conductive wires that are integratedwith a glass back-sheet of the solar cell module.

DETAILED DESCRIPTION OF THE INVENTION

To the extent permitted by the United States law, all publications,patent applications, patents, and other references mentioned herein areincorporated by reference in their entirety.

The materials, methods, and examples herein are illustrative only andthe scope of the present invention should be judged only by the claims.

Definitions

The following definitions are used herein to further define and describethe disclosure.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

As used herein, the terms “a” and “an” include the concepts of “at leastone” and “one or more than one”.

Unless stated otherwise, all percentages, parts, ratios, etc., are byweight.

When the term “about” is used in describing a value or an end-point of arange, the disclosure should be understood to include the specific valueor end-point referred to.

As used herein, the terms “sheet”, “layer” and “film” are used in theirbroad sense interchangeably. A “front sheet” is a sheet, layer or filmon the side of a photovoltaic module that faces a light source and mayalso be described as an incident layer. Because of its location, it isgenerally desirable that the front sheet has high transparency to theincident light. A “back-sheet” is a sheet, layer or film on the side ofa photovoltaic module that faces away from a light source, and isgenerally opaque. In some instances, it may be desirable to receivelight from both sides of a device (e.g., a bifacial device), in whichcase a module may have transparent layers on both sides of the device.

As used herein, “encapsulant” layers are used to encase the fragilevoltage-generating photoactive layer, to protect it from environmentalor physical damage, and hold it in place in the photovoltaic module.Encapsulant layers may be positioned between the solar cell layer andthe front incident layer, between the solar cell layer and theback-sheet, or both. Suitable polymer materials for the encapsulantlayers typically possess a combination of characteristics such as hightransparency, high impact resistance, high penetration resistance, highmoisture resistance, good ultraviolet (UV) light resistance, good longterm thermal stability, good long term weatherability, and adequateadhesion strength to frontsheets, back-sheets, other rigid polymericsheets and solar cell surfaces.

As used herein, “inter layer dielectric” (ILD) is a layer of a lowdielectric constant k material used to electrically separate closelyspaced electrically conductive layers or lines arranged in severallevels of an electrical circuit or device such as a photovoltaic module.

As used herein, the terms “photoactive” and “photovoltaic” may be usedinterchangeably and refer to the property of converting radiant energy(e.g., light) into electric energy.

As used herein, the terms “photovoltaic cell” or “photoactive cell” or“solar cell” mean an electronic device that converts radiant energy(e.g., light) into an electrical signal. A photovoltaic cell includes aphotoactive material layer that may be an organic or inorganicsemiconductor material that is capable of absorbing radiant energy andconverting it into electrical energy. The terms “photovoltaic cell” or“photoactive cell” or “solar cell” are used herein to includephotovoltaic cells with any types of photoactive layers including,crystalline silicon, polycrystalline silicon, microcrystal silicon, andamorphous silicon-based solar cells, copper indium (gallium) diselenidesolar cells, cadmium telluride solar cells, compound semiconductor solarcells, dye sensitized solar cells, and the like.

As used herein, the term “photovoltaic module” or “solar module” (also“module” for short) means an electronic device having at least onephotovoltaic cell protected on one side by a light transmitting frontsheet and protected on the opposite side by an electrically insulatingprotective back-sheet.

As used herein, the term “back-contact solar cell” means a solar cellhaving both positive and negative polarity contacts located on its backside, including metal wrap through (MWT), metal wrap around (MWA),emitter wrap through (EWT), emitter wrap around (EWA), andinterdigitated back contact (IBC) solar cells.

Disclosed herein are back-contact solar modules with a glass back-sheetand integrated conductive wire circuitry and processes for forming suchback-contact solar modules with integrated circuitry.

Arrays of back-contact solar cells are shown in FIGS. 2 a and 2 b. Thedisclosed glass back-sheet and conductive circuitry is useful forprotecting and electrically connecting back-contact solar cell arrayslike those shown in FIGS. 2 a and 2 b. The solar cell array 21 shown inFIG. 2 a includes multiple solar cells 22, such as single crystalsilicon solar cells. The front side (not shown) of each solar cell 22 isadhered to an encapsulant layer 24 that is or will be preferably adheredto a transparent front sheet (not shown) of the solar module. Solarmodules with an array of twelve solar cells 22 are shown in FIGS. 2 aand 2 b, but the disclosed integrated back-sheet is useful as aback-sheet for back-contact solar modules having solar cell arrays ofanywhere from four to more than 100 solar cells.

Each of the solar cells 22 has multiple positive and negative polaritycontacts on back side of the solar cell. The contacts on the back sideof the solar cells are typically made of a metal to which electriccontacts can be readily formed, such as silver or platinum contact pads.The contacts are typically formed from a conductive paste comprising anorganic medium, glass frit and silver particles, and optionallyinorganic additives, which is fired at high temperature to form metalcontact pads. The solar cells shown in FIGS. 2 a and 2 b each have acolumn of four negative polarity contacts and a column of four positivepolarity contacts, but it is contemplated that the solar cells couldhave multiple columns of negative and positive polarity contacts andthat each column could have anywhere form two to more than twentycontacts. In the solar cell array shown in FIG. 2 a, the contacts ofeach cell are arranged in the same way. The arrangement shown in FIG. 2a is used with the disclosed glass back-sheet and conductive circuitrywhen the cells are connected in parallel. Alternatively, the solar cellsin each column of the array can be arranged such that the alternatingcells in each column are rotated 180 degrees as shown in FIG. 2 b. Thesolar cell array 23 shown in FIG. 2 b is used with the disclosed glassback-sheet and conductive circuitry is used to connect the solar cellsin series, as will be described more fully below.

FIG. 3 a shows an embodiment of the disclosed integrated back-sheet. Theintegrated back-sheet 30 shown in FIG. 3 a comprises a glass back-sheet32, a polymeric wire mounting layer 38, and conductive wires 42 and 44.The glass sheet 32 has a surface that faces the wire mounting layer 38and an opposite side that forms an exposed surface on the back of aphotovoltaic module into which the back-sheet is incorporated. The glasssheet 32 is preferably made of a strong shatter proof glass. Thethickness of the glass depends in part on area of the module and theinherent strength of the glass material. For back-contact photovoltaicmodules with typical areas of from 1 to 2 m², a back-sheet glassthickness of from 1.5 mm to 4 mm is preferred. The term “glass” is meantto include not only window glass, plate glass, silicate glass, sheetglass, low iron glass, tempered glass, tempered CeO-free glass, andfloat glass, but also includes colored glass, specialty glass whichincludes ingredients to control, for example, solar heating, coatedglass with, for example, sputtered metals, such as silver or indium tinoxide, for solar control purposes, E-glass and the like. Low lead glassis preferred for environmental reasons. When glass is used for theback-sheet, it may be possible to replace a glass front sheet with aflexible front sheet such as a polymeric front sheet in a rigidphotovoltaic module. Because the back-sheet is not required to be highlytransparent in most instances, as is the case with a front sheet glass,the use of a glass back-sheet rather than a glass front sheet makes itpossible to use a less specialized and less costly glass sheet in themodule. The type of glass to be selected for a particular laminatedepends on the intended use.

In the embodiment of the disclosed integrated glass back-sheet 30 shownin FIG. 3 a, multiple wires are adhered or partially embedded in thewire mounting layer 38 in a generally parallel arrangement. Where theback-sheet is used to connect like mounted solar cells like those shownin FIG. 2 a, each set of wires 42 and 44 connect to negative andpositive contacts, respectively, of a column of solar cell contacts soas to electrically connect the column of cells in parallel. Were theintegrated back-sheet is used to connect solar cells in series, everyother cell in a column of cells can be rotated 180 degrees as shown inFIG. 2 b and the wires 42 and 44 can be selectively cut to connectadjacent cells in series in a column of solar cells as more fullydescribed below.

In the integrated back-sheet 31 shown in FIG. 3 b, a wire mounting layeris provided on the glass back-sheet 32. The wire mounting layer 38 holdsthe wires 42 and 44 in place and attaches them to the glass sheet 32.The wires 42 and 44 are adhered to the surface or partially embedded inthe wire mounting layer with a surface of the wires 42 and 44 beingexposed. The wire 42 is more deeply embedded in the wire mounting layerat places where the wires 42 and 44 cross paths or an insulating pad isinserted between the wires at the cross over points. When the solarcells are connected in parallel, the wire 42 is connected to the solarcell back contacts of one polarity and the wire 44 is connected to thesolar cell back contacts of the opposite polarity. The wires 42 and 44may be embedded under the surface of the wire mounting layer 38 in whichcase the wire mounting layer 38 will have holes formed in it at pointswhere the wires 42 and 44 make electrical contact with solar cell backcontacts. Such holes may be formed, for example, by stamping or diecutting.

The wire mounting layer 38 preferably comprises a polymeric materialsuch as a thermoplastic or thermoset material. The wire mounting layer38 preferably has a thickness sufficient to be self supporting andsufficient to support wires mounted on the wire mounting layer. Forexample, the wire mounting layer typically has a thickness in the rangeof 1 mils to 25 mils, and more preferably in the range of 4 mils to 18mils. The wire mounting layer can include more than one layer of polymermaterial, wherein each layer may include the same material or a materialdifferent from the other layer(s). The wire mounting layer may becomprised of polymer with adhesive properties, or an adhesive coatingcan be applied to the surface(s) of the wire mounting layer to hold thewires in place. The side of the wire mounting layer opposite to theelectrically conductive wires attaches to the glass back-sheet. The wiremounting layer may be formed of a polymeric material that adheresdirectly to the glass back-sheet during thermal lamination of thephotovoltaic module. Alternatively, adhesives such as reactive adhesives(e.g., polyurethane, acrylic, epoxy, polyimide, or silicone adhesives)or non-reactive adhesives (e.g., polyethylenes (including ethylenecopolymers) or polyesters) can be used to attach the wire mounting layerto the glass back-sheet.

Depending upon when the conductive wires are anchored to the backcontacts of the solar cells, it may be desirable for the wire mountinglayer to be made of a polymer that does not melt or deform when thephotovoltaic module is laminated. As more fully discussed below, whenthe conductive wires have already been anchored to the solar cell backcontacts prior to lamination of the photovoltaic module, it may be lessof an issue if the wire mounting layer deforms or melts duringlamination of the photovoltaic module. If, on the other hand, theconductive wires are anchored to the back contacts of the solar cellsduring the lamination of the photovoltaic module or if the wire mountinglayer must act to electronically insulate the wires from the back sideof the solar cells, it will be important that the wire mounting layernot melt or deform during the module lamination step. Where the wiremounting layer must not melt or deform, the wire mounting layer shouldbe formed of a polymer with a melting temperature that is higher thanthe module lamination temperature. Cross-linked or cured encapsulantmaterials typically have softening and melting temperatures above themodule lamination temperature, which typically range from 120° C. to180° C. Polymeric materials useful in the wire mounting layer includeethylene methacrylic acid and ethylene acrylic acid, ionomers derivedtherefrom, or combinations thereof. Exemplary comonomers that may be inthe precursor acid copolymers include, but are not limited to, methylacrylates, methyl methacrylates, butyl acrylates, butyl methacrylates,glycidyl methacrylates, vinyl acetates, and mixtures of two or morethereof.

The wire mounting layer may also be films or sheets comprisingpoly(vinyl butyral)(PVB), ionomers, ethylene vinyl acetate (EVA),poly(vinyl acetals) (including acoustic grade poly(vinyl acetals)),polyurethanes, polyvinylchlorides, polyethylenes, polyolefin blockelastomers, copolymers of a-olefins and a,β-ethylenically unsaturatedcarboxylic acid esters (e.g., ethylene methyl acrylate copolymers andethylene butyl acrylate copolymers), silicone elastomers, polycarbonateresins, epoxy resins, nylon resins and combinations of two or morethereof. As used herein, the term “ionomer” means and denotes athermoplastic resin containing both covalent and ionic bonds derivedfrom ethylene/acrylic or methacrylic acid copolymers. In someembodiments, monomers formed by partial neutralization ofethylene-methacrylic acid copolymers or ethylene-acrylic acid copolymerswith inorganic bases having cations of elements from Groups I, II, orIII of the Periodic table, notably, sodium, zinc, aluminum, lithium,magnesium, and barium may be used. The term ionomer and the resinsidentified thereby are well known in the art, as evidenced by Richard W.Rees, “Ionic Bonding In Thermoplastic Resins”, DuPont Innovation, 1971,2(2), pp. 1-4, and Richard W. Rees, “Physical 30 Properties AndStructural Features Of Surlyn lonomer Resins”, Polyelectrolytes, 1976,C, 177-197. Other suitable ionomers are further described in Europeanpatent EP1781735, which is herein incorporated by reference.

Ethylene copolymers which may be used as an adhesive in the wiremounting layer are more fully disclosed in PCT Patent Publication No.WO2011/044417 which is hereby incorporated by reference. Such ethylenecopolymers are comprised of ethylene and one or more monomers selectedfrom the group of consisting of C1-4 alkyl acrylates, C1-4 alkylmethacrylates, methacrylic acid, acrylic acid, glycidyl methacrylate,maleic anhydride and copolymerized units of ethylene and a comonomerselected from the group consisting of C4-C8 unsaturated anhydrides,monoesters of C4-C8 unsaturated acids having at least two carboxylicacid groups, diesters of C4-C8 unsaturated acids having at least twocarboxylic acid groups and mixtures of such copolymers, wherein theethylene content in the ethylene copolymer preferably accounts for60-90% by weight. A preferred ethylene copolymer adhesive layer includesa copolymer of ethylene and another a-olefin. The ethylene content inthe copolymer accounts for 60-90% by weight, preferably accounting for65-88% by weight, and ideally accounting for 70-85% by weight of theethylene copolymer. The other comonomer(s) preferably constitute 10-40%by weight, preferably accounting for 12-35% by weight, and ideallyaccounting for 15-30% by weight of the ethylene copolymer. The ethylenecopolymer adhesive layer is preferably comprised of at least 70 weightpercent of the ethylene copolymer. The ethylene copolymer may be blendedwith up to 30% by weight, based on the weight of the adhesive layer, ofother thermoplastic polymers such as polyolefins, as for example linearlow density polyethylene, in order to obtain desired properties.Ethylene copolymers are commercially available, and may, for example, beobtained from DuPont under the trade-name Bynel®.

The wire mounting layer may further contain additives, fillers orreinforcing agents known within the art. Such exemplary additivesinclude, but are not limited to, plasticizers, processing aides, flowenhancing additives, lubricants, pigments, titanium dioxide, calciumcarbonate, dyes, flame retardants, impact modifiers, nucleating agentsto increase crystallinity, antiblocking agents such as silica, thermalstabilizers, hindered amine light stabilizers (HALS), UV absorbers, UVstabilizers, anti-hydrolytic agents, dispersants, surfactants, chelatingagents, coupling agents, adhesives, primers, reinforcement additives,such as glass fiber, and the like. There are no specific restrictions tothe content of the additives and fillers in the wire mounting layer aslong as the additives do not produce an adverse impact on the adhesionproperties or stability of the layer.

A polymeric wire mounting layer 38 is shown in FIG. 4 a. Substantiallyparallel pairs of electrically conductive wires 42 and 44 are shown onthe wire mounting layer. Three pairs of wires 42 and 44 are shown inFIG. 4 a, but it is contemplated that more or fewer pairs of wires couldbe used depending upon the number of columns of solar cells in the solarcell array, and depending on the number of columns of back contacts oneach of the solar cells. It is also contemplated that the spacing of thewires and the wire pairs will depend upon the spacing of the columns ofsolar cells in the array, and on the arrangement and spacing of thecolumns of back contacts on each of the solar cells. The wire mountinglayer is in the form of an elongated strip that covers at least onecolumn of solar cells in the solar cell array, and preferably coversmultiple columns of solar cells in the solar cell array, or may coverall of the columns of solar cells in the solar cell array.

The wires 42 and 44 are preferably conductive metal wires or metal foilstrips. The metal wires are preferably comprised of metal selected fromcopper, nickel, tin, silver, aluminum, indium, lead, and combinationsthereof. In one embodiment, the metal wires are coated with tin, nickelor a solder and/or flux material. Where the wires are coated with asolder and optionally with a flux, the wires can more easily be solderedto the back contacts of the solar cells as discussed in greater detailbelow. For example, aluminium wires may be coated with analuminum/silver alloy that can be easily soldered using conventionalmethods. Where the wires are coated with solder, such as an alloy, thesolder may be coated on the wires along their full length or only on theportions of the wires that will come into contact with the solar cellback contacts in order to reduce the amount of the coating materialused. The conductive wires may be coated with an electrically insulatingmaterial such as a plastic sheath so as to help prevent short circuitsin the solar cells when the wires are positioned over the back of anarray of solar cells. Where the conductive wires are coated with aninsulating material, the insulating material can be formed with breakswhere the wires are exposed to facilitate the electrical connection ofthe wires to the back contacts of the solar cells. Alternatively, theinsulating material may be selected such that it will melt or burn offwhen the wires are soldered or welded to the back contacts on the solarcells. The electrically conductive wires preferably each have a crosssectional area of at least 70 square mils along their length, and morepreferably have a cross sectional area of at least 200 square mils alongtheir length, and more preferably have a cross sectional area of 500 to1200 square mils along their length. This wire cross section providesthe strength, current carrying ability, low bulk resistivity, and wirehandling properties desired for module efficiency and manufacturability.The electrically conductive wires may have any cross sectional shape,but ribbon shaped wires or tabbing wires having a width and thicknesswhere the wire width is at least three times greater than the wirethickness, and more preferably where the wire width is 3 to 15 times thewire thickness, have been found to be especially well suited for use inthe integrated back-sheet because wider wires makes it easier to alignthe wires with the back contacts of the solar cells when the wiremounting layer is applied to an array of back-contact solar cells.

The wire mounting layer 38 should be long enough to cover multiple solarcells, and is preferably long enough to cover all of the solar cells ina column of solar cells in the solar cell array, and may even be longenough to cover columns of solar cells in multiple solar cell arrays, asfor example where the wires are applied to a long strip of the wiremounting layer in a continuous roll-to-roll process. For example, thewire mounting layer and the electrically conductive wires can becontinuously fed into a heated nip where the wires are brought intocontact with and adhered to the wire mounting layer by heating the wiremounting layer at the nip so as to make it tacky. Alternatively, thewire mounting layer can be die extruded with the wires fed into the wiremounting layer during the extrusion process. In another embodiment, thewires and the wire mounting layer can be heated and pressed in a batchlamination press to partially or fully embed the wires into the wiremounting layer. Pressure may be applied to the wires at the heated nipso as to partially or fully embed the conductive wires in the wiremounting layer. Preferably a surface of the wires remains exposed on thesurface of the wire mounting layer after the wire is partially or fullyembedded in the wire mounting material so that it will still be possibleto electrically connect the wires to the back contacts of an array ofback-contact solar cells.

Where the solar cells of the solar cell array will be connected inparallel, the full length wires can be used as shown in FIG. 4 a andsubsequently connected to a column of solar cells like one of the solarcell columns shown in FIG. 2 a. Where the solar cells of the array willbe connected in series, the wires are cut at selected points 45 as shownin FIG. 4 b and connected to a column of solar cells where alternatingcells have been rotated by 180 degrees, like one of the columns of solarcells shown in FIG. 2 b, and as more fully described below. Cutting thewires can be performed by a variety of methods including mechanical diecutting of the wires. The underlying wire mounting layer may also bepunched out at selected locations along with the wires.

In order to prevent electrical shorting of the solar cells, it may benecessary to apply an electrically insulating dielectric materialbetween the conductive wires and the back of the solar cells of theback-contact solar cell array. This dielectric layer is provided tomaintain a sufficient electrical separation between the conductive wiresand the back of the solar cells. The dielectric layer, known as aninterlayer dielectric (ILD), may be applied as a sheet over all of thewires and the wire mounting layer, or it may be applied as strips ofdielectic material over only the electrically conductive wires. It isnecessary to form openings in the ILD, as for example by die cutting orpunching sections of the ILD, that will be aligned over the backcontacts of the solar cells and through which the back contacts will beelectrically connected to the conductive wires. Alternatively, the ILDmay be applied by screen printing. The printing can be on the back sideof the solar cells or on the wire mounting layer and wires, and cancover the entire area between the wire mounting layer and the solar cellarray or just selected areas where the wires are present. A printed ILDlayer can be UV cured after application so that the ILD will remain inplace throughout module lamination and use. Where the ILD is printed, itmay be printed only in the areas where the wires need to be preventedfrom contacting the back of the solar cells. The ILD can be applied tothe wires and the wire mounting layer or it can be applied to the backof the solar cells before the conductive wires and the wire mountinglayer are applied over the back of the solar cell array. Alternatively,the ILD may be applied as strips over the wires on the wire mountinglayer or as strips over the portions of the back side of the solar cellsover which the conductive wires will be positioned. The thickness of theILD will depend in part on the insulating properties of the materialcomprising the ILD, but preferred polymeric ILDs have a thickness in therange of 5 to 500 microns, and more preferably 10 to 300 microns andmost preferably 25 to 200 microns.

Where the conductive wires have a complete insulating coating or sheath,it may be possible to eliminate the ILD between the electricallyconductive wires of the integrated back-sheet and the back side of theback-contact solar cells to which the integrated back-sheet is applied.

An ILD layer is shown in FIG. 5 a. The ILD is in the form of a sheetthat covers at least one column of solar cells in the solar cell array,and preferably covers multiple columns of solar cells in the solar cellarray or more preferably covers all of the columns of solar cells in thesolar cell array. The sheet 50 is preferably comprised of an electricalinsulating material such as a thermoplastic or thermoset polymer, andmay be comprised of one or more of the materials that comprise wiremounting layer 38 as described above. For example, the ILD may be aninsulating polymer film such as a polyester, polyethylene orpolypropylene film. Alternatively, the ILD may be a reinforced polymerlayer such as a glass fiber reinforced epoxy layer. The ILD preferablyhas a melting temperature that is greater than the peak laminationtemperature applied during lamination of the photovoltaic module. TheILD may be made of a porous material such as an open glass or polymermesh or weave through which a melted encapsulant or conductive adhesivecan pass.

An encapsulant layer is preferably provided between the ILD and the backside of the solar cells. Encapsulant layers are used to encase thefragile voltage-generating photoactive layer so as to protect it fromenvironmental or physical damage and hold it in place in thephotovoltaic module. Suitable polymer materials for the encapsulantlayer typically possess a combination of characteristics such as highimpact resistance, high penetration resistance, high moistureresistance, good ultraviolet (UV) light resistance, good long termthermal stability, adequate adhesion strength to other rigid polymericsheets and cell surfaces, and good long term weatherability. The uncuredpolymers that may be used in the wire mounting layer described above canalso be used in encapsulant layers, as for example, ethylene methacrylicacid and ethylene acrylic acid, ionomers derived therefrom, orcombinations thereof. Exemplary comonomers that may be in the precursoracid copolymers include, but are not limited to, methyl acrylates,methyl methacrylates, butyl acrylates, butyl methacrylates, glycidylmethacrylates, vinyl acetates, and mixtures of two or more thereof.Suitable encapsulants include poly(vinyl butyral)(PVB), ionomers,ethylene vinyl acetate (EVA), poly(vinyl acetals) (including acousticgrade poly(vinyl acetals)), polyurethanes, polyvinylchlorides,polyethylenes, polyolefin block elastomers, copolymers of a-olefins anda,β-ethylenically unsaturated carboxylic acid esters (e.g., ethylenemethyl acrylate copolymers and ethylene butyl acrylate copolymers),silicone elastomers, polycarbonate resins, epoxy resins, nylon resinsand combinations of two or more thereof.

In one embodiment, the ILD is comprised of a PET polymer film that iscoated with or laminated to an adhesive or an encapsulant layer such asan EVA film. During lamination, the adhesive or encapsulant layeradheres to the back to the solar cells and serves to seal and protectthe cells while the polyester layer remains intact to serve as aninsulator between the conductive wires and the back of the solar cells.Preferably the ILD and the encapsulant layer are comprised of a materialthat can be die cut or punched, or that can be formed with openings init. The ILD may also be coated with an adhesive, such as a pressuresensitive adhesive, on the side of the ILD that will initially becontacted with the conductive wires and wire mounting layer. Suitableadhesive coatings on the ILD include pressure sensitive adhesives,thermoplastic or thermoset adhesives such as the ethylene copolymersdiscussed above, or acrylic, epoxy, vinyl butryal, polyurethane, orsilicone adhesives. As shown in FIG. 5 b, openings 52 are formed in theILD. These openings will correspond to the arrangement of the solar cellback contacts when the ILD is positioned between the conductive wires ofthe integrated back-sheet and the back of the solar cell array.Preferably, the openings are formed by punching or die cutting the ILD,but alternatively the ILD can be formed with the openings. When anencapsulant layer is used between the ILD and the solar cells, theencapsulant layer will preferably have openings aligned with theopenings in the ILD.

FIGS. 6 a-6 d illustrate in partial cross section the steps of onedisclosed process for making a back-contact solar module with anintegrated glass back-sheet. FIGS. 6 a-6 d show the formation of aportion of a photovoltaic module around one solar cell of a solar cellarray. As shown in FIG. 6 a, a transparent front sheet 54, made of glassor a polymer such as a durable fluoropolymer film, is provided. Thetransparent front sheet typically has a thickness of from 2 to 4 mm forglass front sheet or 50 to 250 microns for polymer front sheet. Therigid glass sheet 32 in the back-sheet makes it possible for the frontsheet 54 to be a flexible and durable polymer film or sheet such as afluoropolymer sheet. Where preventing moisture ingress is of primaryimportance, such as where the solar cells are CIGS solar cells, it maybe desirable for both the front and back sheets to be glass sheets. Afront encapsulant layer 56 may be applied over the front sheet 54. Theencapsulant may be comprised of any of the uncured encapsulant oradhesive materials described above, such as uncured EVA. The frontencapsulant layer typically has a thickness of from 200 to 500 microns.The front encapsulant layer must be transparent to light.

FIGS. 6 a-6 d show one photoactive solar cell 58 of the solar cellarray, such as a crystalline silicon solar cell, provided on theencapsulant layer 56. The solar cell has all of its electrical contactson the back side of the solar cell. The best known types of back-contactsolar cells are metal wrap through (MWT), metal wrap around (MWA),emitter wrap through (EWT), emitter wrap around (EWA), andinterdigitated back contact (IBC). Electrical conductors on the lightreceiving front side of the solar cell (facing the transparent frontsheet) are connected through vias in the solar cell to back sideconductive pads 60, while a back side conductive layer (not shown) iselectrically connected to back side contact pads 61. The back contactpads are typically silver pads fired on the solar cells from aconductive paste of silver particles and glass frit in an organiccarrier medium.

A small portion of a solder or of a polymeric electrically conductiveadhesive is provided on each of the contact pads 60 and 61. The portionsof solder or conductive adhesive are shown as balls 62 in FIG. 6 a. Thesolder may be a conventional solder, such as 60/40 tin lead, 60/38/2 tinlead silver, other known solder alloys, or a low melting point solder,such as low melting point solder containing indium that melts around orbelow 160° C. The conductive adhesive may be any known conductiveadhesive, such as an adhesive comprised of conductive metal particles,such as silver, nickel, conductive metal coated particles or conductivecarbon suspended in epoxies, acrylics, vinyl butryals, silicones orpolyurathanes. Preferred conductive adhesives are aniostropicallyconductive or z-axis conductive adhesives that are commonly used forelectronic interconnections.

FIG. 6 b shows the application of a back encapsulant layer 57 and an ILD50, like the layer shown and described with regard to FIG. 5 b, over theback of the solar cell array. FIG. 6 b also shows the application ofelectrically conductive ribbon-shaped wires 42 and 44 over the backcontacts 60 and 61 of the solar cell 58. The conductive wires 42 and 44are provided on the wire mounting layer 38 as described above. The wiremounting layer 38 shown in FIG. 6 b has holes 53 in the surface that areformed, cut or punched in the wire mounting layer over the areas wherethe conductive wires are to be connected to the back contacts of thesolar cell. As shown in FIG. 6 c, heating pins 65 of a welding apparatus64 are arranged to be applied to the conductive wires through the holes53 in the wire mounting layer 38. The heating pins 65 may be in a springloaded “bed of nails” arrangement so as to be able to contact numerouspoints on the conductive wires at the same time. The pins 65 heat theportions of the wires over the back contacts and can press the wiresinto engagement with the balls 62 of solder or adhesive polymer. Whenthe wires are soldered to the back contacts, the pins 65 heat theportions of the wires over the back contacts of the solar cell to atemperature in the range of about 150° C. to 700° C., and more typically400° C. to 600° C. Solders that melt at lower temperatures, such as 160°C., are also useful in the disclosed process.

As shown in FIG. 6 d, the heated pins 65 are removed and the glass sheet32 is applied over the side of the wire mounting layer 38 that isopposite the wires 42 and 44. The entire stack is then subjected to heatlamination, as for example in a heated vacuum press. The wire mountinglayer 38 becomes adhered between the glass sheet 32 and the ILD 50. Theback encapsulant layer 57 seals the back of the solar cell 58 andadheres the ILD 50 to the back of the solar cell 58.

When a conductive adhesive is used to attach and electrically connectthe conductive wires to the back contacts of the solar cells, theconductive adhesive may be heated above its softening temperature withthe heated pins 65 as described above with regard to FIG. 6 c, but whereconductive adhesive is used in place of the solder. More preferably, theconductive adhesive can be selected to have a softening temperatureclose to the lamination temperature that must be applied to theencapsulant layers during lamination of the module so as to melt andcure the encapsulant and cause the adhesive polymer to electricallyconnect and bond the solar cell back contacts and the conductive wiresduring the thermal lamination of the solar module. In this alternativeembodiment, where the conductive adhesive 62 is softened duringlamination, it is not necessary for the wire mounting layer 38 to haveholes in it through which heating pins can pass. However, when theconductive wires are not bonded to the solar cell back contacts prior tothe heated lamination of the solar module, it may be necessary to useother means to hold the conductive wires 42 and 44 in place duringlamination of the solar module.

This can be accomplished by making the wire mounting layer 38 more rigidby curing the wire mounting layer after the conductive wires are appliedand adhered to the mounting layer and before the solar module laminationsteps. Curing of the wire mounting layer is done by heating the wiremounting layer to a point above the cross linking temperature of acurable polymer that makes up the wire mounting layer in a range of 120to 160° C. for a specified time of 5 to 60 minutes. As shown in FIGS. 7,an additional layer 66 of an encapsulant or a suitable adhesive can beapplied over the cured wire mounting layer 38 before application of theprotective glass sheet 32. When the module is laminated, the layer 66adheres the glass to the cured wire mounting layer 38, and theencapsulant layer 57 seals the back of the solar cell 58 and adheres theILD 50 to the back of the solar cell 58.

FIGS. 8 a and 8 b illustrate an alternative process for holding theconductive wires in place over the solar cell back contacts where aconductive adhesive 62 is used to bond and electrically connect thesolar cell back contacts and the conductive wires. The conductiveadhesive 62 is selected to have a curing temperature that issufficiently below the melting and curing temperature of the encapsulantsuch that conductive adhesive can be cured after the conductive wiresare applied over the solar cell back contacts but before the solarmodule is laminated. For example, the conductive adhesive may beselected to have a curing temperature of from room temperature to about100° C. so that the conductive adhesive can be melted and cured so as tofirmly attach the conductive wires 42 and 44 to the back contacts 60 and61, respectively, before the overall module is laminated. Subsequently,the module is laminated and cured at a higher temperature of about 100to 180° C. during which the wire mounting layer 38 (as shown in FIG. 8a) adheres the glass sheet 32 to the ILD 50. The encapsulant layer 57seals the back of the solar cell 58 and adheres the ILD 50 to the backof the solar cell 58. During module lamination, the conductive wires areheld in place and in contact with the solar cell back contacts by thepre-cured conductive adhesive.

In an alternative embodiment, the ILD can serve as the both the wiremounting layer and as the ILD between the back side of the solar cellsand the conductive wires. As shown in FIG. 9 a, a wire mounting layer 70is provided. The wire mounting layer may be comprised of any of thepolymeric materials described above with regard to the wire mountinglayer 38 of FIG. 4 a. The layer 70 may be a solid polymer sheet, a glassfiber reinforced sheet, or an open mesh or weave into which anencapsulant melt can penetrate. As shown in FIG. 9 b, holes 72 arepunched, die cut or formed in the layer 70 at places that correspond towhere the wire mounting layer will be positioned over the back contactsof a solar cell when the wire mounting layer is placed on the back sideof a solar cell. As shown in FIG. 9 c, conductive wires 42 and 44 areadhered to the uncured wire mounting layer 70 over columns of the holes72. The conductive wires are adhered to or embedded in the surface ofthe wire mounting layer as described above. Where the conductive wireswill be used to connect solar cells in parallel, the continuousconductive wires are used as shown in FIG. 9 c. Where the solar cellsare to be connected in series, the conductive wires are selectively cut.Cutting the wires can be performed by a variety of methods includingmechanical die cutting, rotary die cutting, mechanical drilling, orlaser ablation.

The wire mounting layer is then cured, as for example by heating thewire mounting layer above a temperature where cross-linking occurs inthe wire mounting layer. As shown in FIG. 9 d, an additional wire coverlayer 71, comprised of the same or a similar material as used in theuncured wire mounting layer 70, is applied over the conductive wires andthe wire mounting layer 70. The wire mounting layer 70, the conductivewires 42 and 44, and the wire cover layer 71 can be fed into a heatpress or a nip formed between heated rollers in order to produce thewire containing back-sheet substructure shown in FIG. 9 d. Thissubstructure may be utilized in several ways in the production ofback-contact solar cell modules. The substructure of FIG. 9 d can beadhered to the glass sheet 32 by thermal or adhesive lamination whereinthe exposed surface of the wire cover layer 71 is adhered to the glasssheet. This integrated back-sheet can subsequently be laminated to theback side of a solar cell where the wire mounting layer 70 will beadhered to the back side of the solar cells in a manner such that theholes or openings 72 are positioned over the back contacts of the solarcell. Preferably, a polymeric encapsulant layer with openings alignedwith the holes 72 of the wire mounting layer 70 is inserted between thecured wire mounting layer and the back of the solar cells. A conductiveadhesive can be applied in each of the holes or openings 72 of the wiremounting layer 70 before the wire mounting layer is positioned over theencapsulant layer and the back side of the solar cells such that theconductive adhesive will bond and electrically connect the back contactsof the solar cell to the conductive wires during module lamination.Alternatively, the substructure shown in FIG. 9 d, with conductiveadhesive applied in the holes or openings 72, can be applied to anencapsulant layer with corresponding holes which layer is over the backside of a solar cell array. The conductive adhesive in the holes of thewire mounting layer 70 contacts the back contacts on the back side ofthe solar cells through the holes in the encapsulant layer.

A process for forming a back contact solar cell module with a solarcells connected in series by an integrated back-sheet is shown in FIGS.10 a-10 f. According to this process, a front encapsulant layer 74 isprovided as shown in FIG. 10 a. The front encapsulant layer may becomprised of one of the encapsulant or adhesive sheet materialsdescribed above. The front encapsulant layer may be an independent selfsupporting sheet that can be adhered on its front side to a transparentfront sheet (not shown) such as a glass or polymer front sheet, or itmay be a sheet, coating or layer already adhered on a transparent frontsheet such as a transparent and flexible fluoropolymer film or sheet. Asshown in FIG. 10 b, an array of back contact solar cells 76 and 78 areplaced on the surface of the encapsulant layer 74 opposite to the frontsheet side of the encapsulant layer. The solar cells 76 and 78 areplaced with their front light receiving sides facing against the frontencapsulant layer 74. Each of the solar cells has columns of positiveand negative polarity back contacts with the negative contactsrepresented by the lighter circles 79 and the positive contactsrepresented by darker circles 80 in FIG. 10 b. In the cells 76, in eachpair of back contacts, a positive contact 80 is to the right of anegative contact 79. The cells 78 are rotated 180 degrees such that ineach pair of back contacts, a negative contact 79 is to the right of oneof the positive contacts 80. The cells 76 alternate with the cells 78 inboth the vertical and horizontal directions of the solar cell array. Itis contemplated that in other embodiments, there could be more of thepositive or more of the negative contacts on the solar cells, or thatthere could be more or fewer columns of either the positive or negativeback contacts. While FIG. 10 b shows a cell 76 in the upper left handcorner of the solar cell array, it is contemplated that the cells couldbe arranged with a cell 78 in the upper left hand corner and with acells 76 arranged below and next to the upper left hand corner cell 78.While the solar cell placements 76 and 78 are shown as alternating inboth the vertical and horizontal directions of the array, it is alsocontemplated that in an array of series connected solar cells, the cellplacements 76 and 78 could be alternated only in the vertical direction.

In FIG. 10 c, an encapsulant layer (not shown) and is placed over theback of the solar cell array and an ILD 82 is place over theencapsulant. The encapsulant layer may be comprised of any of thepolymeric encapsulant materials discussed above. The ILD may becomprised of any of the materials described above with regard to the ILD50 shown in FIG. 6 b. The ILD 82 preferably has a thickness of about 1to 10 mils. Holes 84 are preformed, cut or punched in the encapsulantand ILD layers over where the back contacts of the solar cell array willbe located. In FIG. 10 d, the holes or openings in the encapsulant andILD layers are shown filled with a conductive adhesive dabs 85 which maybe screen printed in the holes 84 of the ILD 82, or alternatively may beapplied by syringe or other application method.

In FIG. 10 e, one or more wire mounting layer strips 86 withlongitudinally extending wires 42 and 44, like the wire substructureshown and described with regard to FIG. 4 b, are provided and appliedover the ILD 82. The wires 42 and 44 are provided over sets of positiveand negative back contacts on the solar cells. The side of the wiremounting layer strips 86 on which the wires are exposed is positioned sothat the conductive wires 42 and 44 contact the conductive adhesive dabs85 in the holes of the ILD 82. In one embodiment, the side of the wiremounting layer strips opposite the side on which the wires are mountedis already adhered to a glass sheet like the sheet 32 described above.It is contemplated that all of the conductive wires 42 and 44 requiredfor a module could be adhered to a single wire mounting layer strip thatcovers the entire solar cell array of a solar module.

As shown in FIGS. 10 e and 10 f, one of the wires 42 and 44 have beenselectively cut between each set of solar cells in a column of solarcells in the solar cell array. The wires may be cut by mechanical diecutting, rotary die cutting, mechanical drilling or laser ablation.Cutting of the wires may also be performed by punching a hole throughboth the wire and the wire mounting layer, which hole will be filledduring module lamination by polymer flowing from the wire mounting layeror from the encapsulant or adhesive layer between the wire mountinglayer and the glass back-sheet. As shown in FIG. 10 e, the wires 42 arepositioned over columns of the solar cell back-contacts 79 of negativepolarity that can be seen in FIG. 10 b, and the wires 44 are positionedover the columns of back-contacts 80 of positive polarity of the solarcell 76 shown in FIG. 10 b in the upper left corner of the solar cellarray. The wires 42 are cut between where the wires 42 contact the solarcell 76 and where they contact the solar cell 78 which has been rotated180 degrees and that is positioned below the cell 76. The wires 44 whichare positioned over the positive polarity contacts on the upper leftsolar cell 76 runs continuously over the negative contacts on the solarcell 78 positioned below the upper left solar cell 76 so as to connectthe positive polarity contacts of the one cell in series to the negativepolarity contacts of the next cell. The wires 44 are cut between wherethe wires 44 are positioned over the cell 78 and where they arepositioned over the next cell 76 at the bottom right side of the solarcell array that can be seen in FIG. 10 b. On the other hand, the wires42 that are positioned over the positive contacts of the middle cell inthe left hand column of the solar cell array run continuously to wherethe wires 42 are positioned over the negative contacts of the solar cell76 at the bottom right side of the solar cell array as can be seen inFIG. 10 b. This pattern is repeated for as many solar cells as there arein the columns of the solar cell array. In FIG. 10 e, the wires 42 and44 are shown as being attached to four wire mounting layer strips 86,but it is contemplated that the wires could all be mounted, andoptionally precut, on just one or two wire mounting layer strips thatcover the entire solar cell array.

FIG. 10 f shows the application of bus connections 94, 96, and 98 on theends of the solar module. The terminal buss 94 connects to the wires 44that are over and will connect to the positive back-contacts on thesolar cell at the bottom left hand side of the solar cell array.Likewise, the terminal buss 98 connects to the wires 44 that are overthe negative back-contacts on the solar cell at the bottom right handside of the solar cell array. Positive terminal buss 94 is connected toa positive lead 93 and the negative terminal buss 98 is connected to anegative lead 97. The intermediate buss connectors 96 connect thepositive or negative back contacts at the top or bottom of one column ofsolar cells to the oppositely charged contacts at the same end of theadjoining column of solar cells. The terminal buss connections mayalternately be extended through the “Z” direction out through the glassback sheet. This would eliminate the need for extra space at the ends ofthe module for running the buss wires to the junction box. Such “extraspace” would reduce the packing density of the cells and reduce theelectric power output per unit area of the module.

The solar cell array shown in FIG. 10 is simplified for purpose ofillustration and shows only four columns of three solar cells, and eachsolar cell is shown with just three columns of positive and threecolumns of negative back contacts. It is contemplated that the solarcell array of the solar module could have many more columns or rows ofindividual solar cells, and that each solar cell could have fewer ormore columns or rows of back contacts than what is shown in FIG. 10.

The photovoltaic module of FIG. 10 may be produced through autoclave andnon-autoclave processes. For example, the photovoltaic module constructsdescribed above may be laid up in a vacuum lamination press andlaminated together under vacuum with heat and standard atmospheric orelevated pressure. In an exemplary process, a polymer front sheet, afront-sheet encapsulant layer, a back-contact photovoltaic cell layer, aback encapsulant layer, an ILD, a layer of longitudinally extendingwires on a polymeric wire mounting layer, and a glass back sheet asdisclosed above are laminated together under heat and pressure and avacuum (for example, in the range of about 27-28 inches (689-711 mm) Hg)to remove air. In an exemplary procedure, the laminate assembly isplaced into a bag capable of sustaining a vacuum (“a vacuum bag”),drawing the air out of the bag using a vacuum line or other means ofpulling a vacuum on the bag, sealing the bag while maintaining thevacuum, placing the sealed bag in an autoclave at a temperature of about120° C. to about 180° C., at a pressure of from 50 to 250 psig, andpreferably about 200 psi (about 14.3 bars), for from about 10 to about50 minutes. Preferably the bag is autoclaved at a temperature of fromabout 120° C. to about 160° C. for 20 minutes to about 45 minutes. Morepreferably the bag is autoclaved at a temperature of from about 135° C.to about 160° C. for about 20 minutes to about 40 minutes.

Air trapped within the laminate assembly may be removed using a nip rollprocess. For example, the laminate assembly may be heated in an oven ata temperature of about 80° C. to about 120° C., or preferably, at atemperature of between about 90° C. and about 100° C., for about 30minutes. Thereafter, the heated laminate assembly is passed through aset of nip rolls so that the air in the void spaces between thephotovoltaic module outside layers, the photovoltaic cell layer and theencapsulant layers may be squeezed out, and the edge of the assemblysealed. This process may provide a final photovoltaic module laminate ormay provide what is referred to as a pre-press assembly, depending onthe materials of construction and the exact conditions utilized. Thepre-press assembly may then be placed in an air autoclave where thetemperature is raised to about 120° C. to about 160° C., or preferably,between about 135° C. and about 160° C., and the pressure is raised tobetween about 50 psig and about 300 psig, or preferably, about 200 psig(14.3 bar). These conditions are maintained for about 15 minutes toabout 1 hour, or preferably, about 20 to about 50 minutes, after which,the air is cooled while no more air is added to the autoclave. Afterabout 20 minutes of cooling, the excess air pressure is vented and thephotovoltaic module laminates are removed from the autoclave. Thedescribed process should not be considered limiting. Essentially, anylamination process known within the art may be used to produce the backcontact photovoltaic modules with integrated back circuitry as disclosedherein.

If desired, the edges of the photovoltaic module may be sealed to reducemoisture and air intrusion by any means known within the art. Suchmoisture and air intrusion may degrade the efficiency and lifetime ofthe photovoltaic module. Edge seal materials include, but are notlimited to, butyl rubber, polysulfide, silicone, polyurethane,polypropylene elastomers, polystyrene elastomers, block elastomers,styrene-ethylene-butylene-styrene (SEBS), and the like.

While the presently disclosed invention has been illustrated anddescribed with reference to preferred embodiments thereof, it will beappreciated by those skilled in the art that various changes andmodifications can be made without departing from the scope of thepresent invention as defined in the appended claims.

What is claimed is:
 1. A process for making an integrated back-sheet fora back contact solar cell module with a plurality of electricallyconnected solar cells, comprising: providing a polymeric wire mountinglayer having opposite first and second sides and having a lengthwiselength and direction and a crosswise direction perpendicular to thelengthwise direction; providing a plurality of elongated electricallyconductive wires and adhering said plurality of electrically conductivewires to the first side of said polymeric wire mounting layer in thelengthwise direction of said polymeric wire mounting layer, saidelectrically conductive wires being substantially aligned with thelengthwise direction of said polymeric wire mounting layer, saidplurality of electrically conductive wires each having a cross sectionalarea of at least 70 square mils along their length, said plurality ofelectrically conductive wires not touching each other upon being adheredto said polymeric wire mounting layer, and said plurality ofelectrically conductive wires extending at least two times the length ofa solar cell of the back-contact solar cell module; providing a glassback-sheet, and adhering said second side of said polymeric wiremounting layer to said glass back-sheet; providing a polymericinterlayer dielectric layer having opposite first and second sides andhaving a lengthwise length and direction and a crosswise directionperpendicular to the lengthwise direction, and forming openings in saidpolymeric interlayer dielectric layer, said openings being arranged in aplurality of columns extending in the lengthwise direction of saidpolymeric interlayer dielectric layer; arranging the plurality ofcolumns of openings in said interlayer dielectric layer over theelectrically conductive wires adhered to the wire mounting layer suchthat the openings in each column of openings are aligned with and overone of the plurality of electrically conductive wires; and attaching thepolymeric interlayer dielectric layer to polymeric wire mounting layer.2. The process for making an integrated back-sheet of claim 1 whereinsaid glass back-sheet has a thickness of from 1.5 to 4 mm.
 3. Theprocess for making an integrated back-sheet of claim 1 wherein thepolymeric wire mounting layer is cured before the polymeric interlayerdielectric layer is attached to the wire mounting layer.
 4. The processfor making an integrated back-sheet of claim 3 wherein after theelectrically conductive wires are adhered to the polymeric wire mountinglayer, the polymeric wire mounting layer is cured by heating thepolymeric wire mounting layer to the curing temperature of the polymericwire mounting layer.
 5. The process for making an integrated back-sheetof claim 1 wherein said polymeric wire mounting layer is comprised of apolymer selected from poly(vinyl butyral), ionomers, ethylene vinylacetate, poly(vinyl acetal), polyurethane, poly(vinyl chloride),polyolefins, polyolefin block elastomers, ethylene acrylate estercopolymers, ethylene copolymers, silicone elastomers, polycarbonateresins, epoxy resins, nylon resins and combinations thereof.
 6. Theprocess for making an integrated back-sheet of claim 5 wherein saidpolymeric wire mounting layer is an ethylene copolymer comprised ofethylene and one or more monomers selected from the group of consistingof C1-4 alkyl acrylates, C1-4 alkyl methacrylates, methacrylic acid,acrylic acid, glycidyl methacrylate, maleic anhydride and copolymerizedunits of ethylene and a comonomer selected from the group consisting ofC4-C8 unsaturated anhydrides, monoesters of C4-C8 unsaturated acidshaving at least two carboxylic acid groups, diesters of C4-C8unsaturated acids having at least two carboxylic acid groups andmixtures of such copolymers, wherein the ethylene content in theethylene copolymer accounts for 60-90% by weight.
 7. The process formaking an integrated back-sheet of claim 1 wherein said polymericinterlayer dielectric layer is comprised of poly(vinyl butyral),ionomers, ethylene vinyl acetate, poly(vinyl acetal), polyurethane,poly(vinyl chloride), polyolefins, polyolefin block elastomers, ethyleneacrylate ester copolymers, ethylene copolymers, silicone elastomers,chlorosulfonated polyethylene, epoxy and combinations thereof.
 8. Theprocess for making an integrated back-sheet of claim 1 furthercomprising the step of selectively cutting one or more of saidelectrically conductive wires at one or more selected points along thelength of said electrically conductive wires.
 9. A process for making aback-contact solar cell module, comprising: providing a solar cell arrayof at least four solar cells each having a front light receivingsurface, an active layer that generates an electric current when saidfront light receiving surface is exposed to light, and a rear surfaceopposite said front surface, said rear surface having positive andnegative polarity electrical contacts thereon, at least two of the solarcells of the solar cell array arranged in a column; providing apolymeric wire mounting layer having opposite first and second sides andhaving a lengthwise direction and a crosswise direction perpendicular tothe lengthwise direction; providing a plurality of elongatedelectrically conductive wires and adhering said plurality ofelectrically conductive wires to the first side of said polymeric wiremounting layer in the lengthwise direction of said polymeric wiremounting layer, said electrically conductive wires being substantiallyaligned with the lengthwise direction of said polymeric wire mountinglayer, said plurality of electrically conductive wires each having across sectional area of at least 70 square mils along their length, saidplurality of electrically conductive wires not touching each other uponbeing adhered to said polymeric wire mounting layer, and said pluralityof electrically conductive wires extending at least the length of acolumn of the solar cells in the solar cell array; providing a polymericinterlayer dielectric layer having opposite first and second sides andhaving a lengthwise length and direction and a crosswise directionperpendicular to the lengthwise direction, and forming openings in saidpolymeric interlayer dielectric, said openings being arranged in aplurality of columns extending in the lengthwise direction of saidpolymeric interlayer dielectric layer; placing the interlayer dielectriclayer between the rear surface of the solar cells of the solar cellarray and the first side of the wire mounting layer, and arranging theplurality of columns of openings in said interlayer dielectric layerover the electrically conductive wires adhered to the wire mountinglayer such that the openings in each column of openings are aligned withand over one of the plurality of electrically conductive wires, andaligning the openings in said interlayer dielectric layer with thepositive and negative polarity contacts on the rear surfaces solar cellsof the solar cell array, wherein said positive and negative polarityelectrical contacts on said solar cells are electrically connected tosaid electrically conductive wires through the openings in saidpolymeric interlayer dielectric layer; adhering said polymericinterlayer dielectric layer to said first surface of the polymeric wiremounting layer and to said rear surface of the solar cells of the solarcell array; providing a glass back-sheet, and attaching said second sideof said polymeric wire mounting layer to said glass back-sheet.
 10. Theprocess for making a back-contact solar cell module of claim 9 whereinthe polymeric wire mounting layer is cured before the polymericinterlayer dielectric layer is attached to the wire mounting layer. 11.The process for making a back-contact solar cell module of claim 10wherein after the electrically conductive wires are adhered to thepolymeric wire mounting layer, and the polymeric wire mounting layer iscured by heating the polymeric wire mounting layer to the curingtemperature of the polymeric wire mounting layer.
 12. The process formaking a back-contact solar cell module of claim 9 wherein saidpolymeric wire mounting layer and said interlayer dielectric layer arecomprised of a polymer selected from poly(vinyl butyral), ionomers,ethylene vinyl acetate, poly(vinyl acetal), polyurethane, poly(vinylchloride), polyolefins, polyolefin block elastomers, ethylene acrylateester copolymers, ethylene copolymers, silicone elastomers,polycarbonate resins, epoxy resins, nylon resins and combinationsthereof.
 13. An integrated back sheet for a solar cell module with aplurality of electrically connected solar cells, comprising: a polymericwire mounting layer having opposite first and second sides and having alengthwise length and direction and a crosswise direction perpendicularto the lengthwise direction, said polymeric wire mounting layer having alength of at least two times the length of a solar cell in the solarcell module; a plurality of elongated electrically conductive wiresadhered to the first side of said polymeric wire mounting layer in thelengthwise direction of said polymeric wire mounting layer, saidelectrically conductive wires being substantially aligned with thelengthwise direction of said polymeric wire mounting layer, saidplurality of electrically conductive wires each having a cross sectionalarea of at least 70 square mils along their length, said plurality ofelectrically conductive wires not touching each other upon being adheredto said polymeric wire mounting layer, and said plurality ofelectrically conductive wires extending at least two times the length ofa solar cell in the solar cell module, at least one of said electricallyconductive wires being cut at at least one selected point along thelength of said electrically conductive wires; and a glass back-sheetattached to the second side of said polymeric wire mounting layer.
 14. Asolar cell module, comprising: a solar cell array of at least four solarcells arranged in at least one column having a length, each of saidsolar cells having a front light receiving surface, an active layer thatgenerates an electric current when said front light receiving surface isexposed to light, and a rear surface opposite said front light receivingsurface, said rear surfaces having positive and negative polarityelectrical contacts thereon; a polymeric wire mounting layer havingopposite first and second sides and having a lengthwise direction and acrosswise direction perpendicular to the lengthwise direction; aplurality of elongated electrically conductive wires adhered to thefirst side of said polymeric wire mounting layer in the lengthwisedirection of said polymeric wire mounting layer, said electricallyconductive wires being substantially aligned with the lengthwisedirection of said polymeric wire mounting layer, said plurality ofelectrically conductive wires each having a cross sectional area of atleast 70 square mils along their length, said plurality of electricallyconductive wires not touching each other, and said plurality ofelectrically conductive wires extending at least the length of a columnof the solar cells in the solar cell array; a polymeric interlayerdielectric layer having opposite first and second sides and having alengthwise length and direction and a crosswise direction perpendicularto the lengthwise direction, said polymeric interlayer dielectric layerhaving openings arranged in a plurality of columns extending in thelengthwise direction of said polymeric interlayer dielectric layer; saidinterlayer dielectric layer adhered to the rear surface of the solarcells of the solar cell array and to the first side of the wire mountinglayer, wherein the plurality of columns of openings in said interlayerdielectric layer are arranged over the electrically conductive wiresadhered to the wire mounting layer such that the openings in each columnof openings are aligned with and over one of the plurality ofelectrically conductive wires, and wherein the openings in saidinterlayer dielectric layer are aligned with the positive and negativepolarity contacts on the rear surfaces solar cells of the solar cellarray, wherein said positive and negative polarity electrical contactson the rear surface of said solar cells are electrically connected tosaid electrically conductive wires through the openings in saidpolymeric interlayer dielectric layer; and a glass back-sheet attachedto said second side of said polymeric wire mounting layer.
 15. The solarcell module of claim 14 wherein said polymeric wire mounting layer andsaid interlayer dielectric layer are comprised of a polymer selectedfrom poly(vinyl butyral), ionomers, ethylene vinyl acetate, poly(vinylacetal), polyurethane, poly(vinyl chloride), polyolefins, polyolefinblock elastomers, ethylene acrylate ester copolymers, siliconeelastomers, polycarbonate resins, epoxy resins, nylon resins andcombinations thereof.
 16. The solar cell module of claim 14 wherein saidglass back-sheet has a thickness of from 1.5 to 4 mm.
 17. The solar cellmodule of claim 14 wherein the electrically conductive wires arecomprised of metal selected from copper, nickel, tin, silver, aluminum,and combination thereof, and wherein the electrically conductive wiresare ribbon-shaped metal wires having a width and thickness wherein thewire width is at least three times greater than the wire thickness. 18.A solar cell module, comprising: a solar cell array of at least foursolar cells each having a front light receiving surface, an active layerthat generates an electric current when said front light receivingsurface is exposed to light, and a rear surface opposite said frontlight receiving surface, said rear surface having positive and negativepolarity electrical contacts thereon, said solar cell array having alength and width; a glass back-sheet, having first and second oppositesides, said glass back sheet having a length greater than or equal tothe length of said solar cell array and a width greater than or equal tothe width of said solar cell array; a plurality of electricallyconductive wires disposed between said glass back-sheet and said solarcell array and supported by said first side of said glass back-sheet,said electrically conductive wires being substantially aligned with thelength of the glass back-sheet, said electrically conductive wireshaving a length of at least two times the length of a solar cell of thesolar cell array, and said electrically conductive wires having a crosssectional area of at least 70 square mils along their length, saidplurality of electrically conductive wires not touching each other; apolymeric insulating layer having opposite first and second sidesdisposed between said plurality of electrically conductive wires andsaid solar cell array, said first side of said polymeric insulatinglayer being adhered to the rear surface of the solar cells of the solarcell array and said second side of said polymeric insulating layer beingadhered to said plurality of electrically conductive wires, saidpolymeric insulating layer having openings over the positive andnegative contacts on the rear surface of the solar cells of the solarcell array, wherein said positive and negative contacts on said solarcells are electrically connected to one of said electrically conductivewires through the opening in said polymeric insulating layer over theelectrical contacts.
 19. The solar cell module of claim 18 wherein saidsecond side of said polymeric insulating layer is adhered to said firstside of said glass back-sheet.
 20. The solar cell module of claim 18,further comprising a polymeric encapsulant layer, said polymericencapsulant layer disposed between said plurality of electricallyconductive wires and said first side of said glass back-sheet, saidpolymeric encapsulant layer having opposite first and second sides, thefirst side of said polymeric encapsulant layer being adhered to thesecond side of the polymeric insulating layer such that the plurality ofelectrically conductive wires are sandwiched between said polymericencapsulant layer and said polymeric insulating layer, and the secondside of said polymeric encapsulant layer being adhered to said firstside of said glass back-sheet.